The more stringent air quality standards, recently enacted, have meant that more coal burning combustors must install sulfur dioxide (SO.sub.2) removal systems for the stack gases. One popular method is to utilize a lime solution [CaOH).sub.2 ] with the stack gases bubbling through a film of the solution in a scrubber. In the scrubber, the sulfur dioxide (SO.sub.2) in the stack gas reacts with the lime solution [Ca(OH).sub.2 ] to form calcium sulfate half-hydrate (plaster of Paris) [CaSO.sub.4.1/2H.sub.2 O] in the residue collected at the bottom of the scrubber. In the residue is also residual lime solution [Ca(OH).sub.2 ]. This residue is very difficult to handle and is normally filtered on a belt, leaf or drum filter to remove as much water as possible. The remaining filter cake contains from 10 to 20% water by weight and is very difficult to handle.